Tell her you would love to buy her some sexy clothes to hot her wardrobe up, so she can feel her best for dating a lover of her choice when she feels ready.
Only 1% of guys have the really big cocks, so if you stretch her too much, you might have trouble finding a guy with a compatible cock.
Go with the flow, and work more fingers in as she suggests. She is accepting sexual changes, so things are looking up.
Be careful to not keep harping on her fucking a lover, because she can feel angry if she is feeling you forcing her to set aside her wedding vows.
Girls accept change when they are ready to, when the idea has been growing at the back of their mind for awhile. It takes time, and they often are guided by what their friends are doing.
A wife can be seriously worried that you might be wanting to "jump another girl" if they agree to taking a lover. That is a threat to the marriage.
They need to feel that you will love them the same, even if they are topping up with the lover.
And when she takes a lover, there will be no turning back, because you have conditioned her mind to now believe that you marriage is now "you, her and other guys". Her primal urges will surface that she does not even know exist, and she won't be able to be a "prim and proper wife" again. The extra sex will become a permanent new craving, and some of these bulls might want a lot of her time.
As girls grow up, they are taught by their mothers to not let boys see their panties or nakedness, so if you encourage her to take her pants off for another guy, you create a precedent which allows her to emotionally have no reason to hide her nakedness any more.
You have said that "to have and to hold to the exclusion of others" does not apply any longer - and therefore your marriage is now polymory for her and monogamous for you - which means you are fast becoming a cuckold.
